Thousands of prehistoric stone jars, many of megalithic proportions, are grouped in clusters across the Xieng Khouang Plateau, 1,000 metres above sea level in north-central Laos. To date, some 50 jar fields have been identified, usually situated on promontories and other strategically high places; some sites contain more than 250 individual jars. The Plain of Jars is one of the most important sites for studying the late prehistory of mainland South East Asia. At two of the sites earthenware jars have been found containing human bones, reinforcing the view that the jars themselves were used to hold the remains of the dead, with the larger jars perhaps reserved for the aristocracy. Scholars postulate that the bodies were first interred in the giant stone urns which were sealed with carved lids, then later disinterred, cremated, and finally buried in earthenware jars. Both stone jars and earthenware urns were decorated with motifs such as cats, stars, or the raised-arm figure that the modern Lao call the ‘frog man’. Today it is believed that the people who created the Plain of Jars were the descendants of those who created the menhirs of Houaphanh Province; there is some similarity in the grave offerings, and also a similarity between the stone discs that covered the entrances to the grave shafts in Houaphanh Province and the carved lids of the jars in Xieng Khouang. It is believed that the transition from the rough upright standing stones of Houaphanh Province to the carefully hewn jars of Xieng Khouang came with the use of iron tools - the advent of iron forging in around the 4th century BCE offered new creative opportunities to the prehistoric necropolis builders. Some of the grave-goods found in the jars indicate that the Plain of Jars civilisation engaged in international trade with China, India and neighbouring societies. The Plain of Jars is rich in salt, and it is likely that this commodity, highly valued at the time, secured its place on international trade routes. Iron objects found close by date the Plain of Jars civilisation from the 4th century BCE to the 2nd century CE. Unfortunately the Plain of Jars remains one of the world's most endangered archaeological sites in the world. The recently initiated UNESCO-Lao Project to Safeguard the Plain of Jars aims to remove the danger of unexploded ordnance, help to rehabilitate the plateau's agricultural land and identify priority areas for protection for archaeological research and tourism development. One of the principal tools used for this work is a precise GIS (geographical information system) map of the Plain of Jars. The GIS map will provide vital information for de-mining operations as well as the geo-coding of archaeological resources. The map will also provide the basis of a culture resource management plan for the province of Xieng Khouang which will facilitate the nomination of three of the Plain of Jars sites to the UNESCO World Heritage List in 2005, thus effectively placing the area under permanent international protection. To accomplish these tasks, the UNESCO-Lao team is undertaking to map every square metre of the plateau using remote sensing technology and computerised geographical information systems (GIS). Data concerning known aerial bombardments and areas which have already been cleared of UXO are incorporated in the GIS database. Field survey teams from each village and district then set out to locate all jar fields and other ancient sites. In each location they establish permanent geodetic control points which link the archaeological sites into the GIS data base. These sites are scheduled for priority UXO clearance. Closely following the clearance teams, archaeologists working with the local survey teams determine the precise location and dimension of each individual jar and include this geo-coded information into the GIS data base. The result, when completed, will be a composite, computer-based, three-dimensional map of the entire Plain of Jars. This map will serve as the principal planning tool for future development in Xieng Khouang. It will guide archaeological research and tourism development in the Plain of Jars as well as integrating agricultural land rehabilitation and new settlements into this ancient land. Collaborators include the Ministry of Information and Culture, the Xieng Khouang Provincial Government, the Department of Integrated Natural Resources Data and Science and Technology Information, the Science, Technology and Environment Agency (STEA), the Lao National Mekong Committee (NMC), the Lao Unexploded Ordnance Project (UXO Laos), Handicap International, the Environmental Systems Research Institute Inc (ESRI), the Lao National Commission for UNESCO, the UNESCO World Heritage Centre and the UNESCO Principal Regional Office for Asia and the Pacific (PROAP).